Gynogenesis and Hybridization between Ambystoma platineum and Ambystoma texanum in Illinois

Abstract

Two kinds of virtually unisexual, polyploid Ambystoma occur at Kickapoo State Park, Vermilion County Illinois. One is the triploid (3n = 42) A. platineum. The other is a tetraploid (4n = 56) hybrid A. platineum .times. A. texanum. Eggs of A. platineum from this locality do not cleave unless inseminated. There are no diploid members of the A. jeffersonianum complex at the site, so triploids must be gynogenetic sexual parasites of A. texanum or A. maculatum. In artificial insemination experiments, 59% of 214 eggs from A. platineum inseminated with A. texanum or A. maculatum sperm failed in or before gastrulation. Sizes of ectodermal nuclei of arrested embryos indicated they were tetraploid. There is partial incompatibility between A. platineum and the other 2 spp., although A. texanum was more compatible than A. maculatum. Larvae hatched only from eggs inseminated with A. texanum sperm and 3 of 4 were triploid (the 4th was not determined). A. platineum did not court with males of either A. texanum or A. maculatum, but engaged in courtship-like behavior with each other, possibly to induce ovulation or oviposition. In nature, they probably mount spermatophores encountered in fields deposited by A. texanum.